The disclosure relates generally to distribution of communications signals in a distributed antenna system (DAS) and, more particularly, to reducing leaked downlink interference signals in an uplink path(s) in the DAS resulting from downlink and uplink communications in a remote unit.
Wireless customers are increasingly demanding digital data services, such as streaming video signals. Concurrently, some wireless customers use their wireless devices in areas that are poorly serviced by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of DASs. DASs can be particularly useful when deployed inside buildings or other indoor environments where client devices may not otherwise be able to effectively receive radio frequency (RF) signals from a source. DASs include remote antenna units (RAUs) configured to receive and transmit communications signals to client devices within the antenna range of the RAUs.
A typical DAS comprises head-end equipment (HEE) communicatively coupled to a plurality of remote units. If the remote units include antennas to support transmission and reception of wireless communications signals, the remote units may be referred to as RAUs. The HEE is typically communicatively coupled to a cellular base station. The HEE is configured to distribute received downlink communications signals from the cellular base station to the RAUs. The RAUs are configured to distribute received uplink communications signals received from client devices to the HEE to be provided to the cellular base station. The HEE is configured to receive and support a variety of wireless communications services for distribution to the RAUs, such as wideband code division multiple access (WCDMA), long term evolution (LTE), and wireless local area network (WLAN) communications services as examples. To distribute the wireless communications services in the DAS, the wireless communications services can be provided in the form of analog RF communications signals and/or digital communications signals to the HEE of the DAS for distribution to the RAUs.
An RAU in the DAS may be configured to support more than one type of wireless communications service that operates in a variety of RF spectrums and bandwidths. Downlink wireless communications signals received by the RAU are typically amplified by a signal amplifier to increase signal strength before being distributed to the client devices through one or more coupled antennas. However, the amplified downlink communications signals may include intermodulation products. For instance, if two (2) downlink wireless communications signals operating on an 869 MHz band and an 894 MHz band are amplified by the signal amplifier, intermodulation products may be generated below the 869 MHz band (e.g., 844 MHz, 819 MHz, 794 MHz, and so on) and above the 894 MHz band (e.g., 919 MHz, 944 MHz, 969 MHz, and so on). The intermodulation products should be sufficiently isolated to prevent or reduce interferences on adjacent wireless communication channels.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.